Civil engineers can be found at the very heart of the process of waste and resource management.
Explanation and background
Waste is created by every part of society, from private households to commercial businesses such as the construction industry.
Engineers involved in the waste industry and the process of Resource Management like to encourage the idea of a 'waste hierarchy' of:
- Recover (the process of using waste to generate energy).
Waste should be viewed as a resource. The whole sector aims to extract the highest possible value effectively and efficiently from the waste streams, through reuse and processing waste materials into recycled products, exploiting waste to produce alternative sources of energy, with the aim of minimising the residual waste for eventual disposal.
The waste engineer
On a landfill site you will typically find civil engineers performing a number of functions, including design and oversight of the lining and capping of landfills. They will also be responsible for constructing drainage systems, surface water control systems, road and transport infrastructure.
There will also be technical landfill gas engineers to design and oversee the gas control systems, whilst if there is on site power generation, mechanical and electrical beginners will also be required.
If the treatment technology involves thermal processes, civil and mechanical engineers will help to build these systems, whilst technical process engineers will support their continued operation.
Every modern waste management facility has to be designed and built, and the role of civil engineers in this process is essential. Many of the engineers involved in this will be educated to degree level, and have become members of professional institutions such as ICE.
The waste sector is full of abbreviations and acronyms. Some of the key ones can be found below.
- HRWC - Household Waste Recycling Centre - used by members of the public for large waste items, which can be processed and recycled.
- MRF - Material Recycling Facility - where collected waste is sorted to remove recyclable elements such as wood, glass, paper, card and metals.
- WTS - Waste Transfer Station - where collected waste is brought in from different areas to be transferred onwards to the treatment facility in bulk
- BMW - Biodegradable Municipal Waste - this is the fraction of waste that can decompose and give off green house gases such as carbon dioxide. There is a now a significant effort being made to separate this element from the overall waste stream and to send it for composting or other forms of treatment
- Landfill - Landfill sites, can be with Methane collection - this method of disposing of waste is being phased out for a number of reasons. Simply burying our un-treated waste is unsustainable. Where methane gas is collected from landfills, this can used to generate power through gas engines.
- EfW - Energy from Waste - comprise facilities that are able to generate power from waste by utilising a number of technologies
- AD - Anaerobic Digestion - this is a controlled biological process involving food waste, green garden waste, human waste and animal slurries. Methane is generated under controlled conditions which is then converted into energy through gas driven engines.
- MBT - Mechanical Biologicial Treatment - also a biological process, this time involving the BMW element of general waste. This allows for the waste to be sterilised and dried, to allow for an overall volume and mass reduction. Recyclable materials are also removed and the remaining product can be sent to an EfW incinerator facility to generate power
- SRF / RDF - Sold Recovered Fuel / Refuse Derived Fuel - this is the sold output from various waste treatments, such as MBT
- IVC - In Vessel Composting - biodegradable material that contains raw food and meat products must be composted within an enclosed environment. The composting process is enclosed and controlled with the resulting output of compost available for use in gardens and farms
- Autoclave - effectively like a large pressure cooker where the waste is heated under pressure and sterilised. The output can be used as a fuel in the generation of energy
- Gasification or Pyrolysis - although well established technologies these form part of the newer suite of alternative thermal treatment technologies for treating waste that involve heating waste to temperatures of ~500C in the absence of oxygen (pyrolysis) and temperatures of 1200C in limited oxygen leading to the production of gases which can be used as a source of fuel to generate power.
Whilst there are various different methods for treating waste, there are only two forms of waste infrastructure.
- Local Authority plants - the Waste Disposal Authority, typically a county council, has had a facility built for their own use. Modern facilities will typically have been built with central government support under a Private Finance Initiative (PFI) contract, which involves a large Waste Operator, who will operate the plant for a period of time, typically 25 years
- Merchant Plant - such a facility will be built and owned by a Waste Operator, and charges a 'gate fee' for every load of waste that is brought to the facility. Merchant plants will accept local authority waste and private waste.
Recent years have seen a number of new waste facilities built around the UK, such as the EfW at Lakeside, near Heathrow and 2 MBT plants in East London, near Dagenham. There are a considerable number of facilities currently under construction, such as those within Greater Manchester and an EfW currently under construction on the South Bank of the Thames in East London. There are also lots of other plants currently within the planning process such as those at Basildon, Essex and St Dennis in Cornwall.